A silicone gel composition is an addition curing organopolysiloxane composition which contains an organohydrogenpolysiloxane having a hydrogen atom bound to a silicon atom (i.e., an SiH group), an organopolysiloxane having an alkenyl group such as a vinyl group bound to a silicon atom, and a platinum-based catalyst to give a cured product by an addition reaction of the hydrogen atom bound to a silicon atom to the alkenyl group. The silicone gel cured product cured by heating this silicone gel composition has excellent heat resistance, weather resistance, oil resistance, cold resistance, electrical insulating properties, and so on; has low elastic modulus and low stress; thereby being used for protecting electronic components such as an onboard electronic component and an electronic component for consumer use. Particularly, low elastic modulus and low stress, which are features of a silicone gel cured product, are exclusive features that are not realized by other elastomer products. Recently, heat resistance is increasingly required for a silicone gel cured product used for sealing due to a requirement for high reliability of an onboard electronic component and an electronic component for consumer use.
As a means to improve the heat resistance of a silicone gel cured product, it is disclosed that hydroxyl groups in a composition is reduced to 150 ppm or less (see patent document 1). It is also disclosed that an alkoxysilane compound and an organic titanate ester are contained in a composition with a particular organopolysiloxane (see patent document 2). Furthermore, it is disclosed that a reaction product obtained by a heat treatment of a particular metal carboxylate salt and an organopolysiloxane at a high temperature is contained in a composition (see patent document 3), and so on.